1. Field of the Invention
The present invention relates generally to a potable water delivery system wherein hot water is circulated to a user outlet and more particularly to a potable water delivery system wherein water in the higher temperature water supply pipe is circulated into the lower temperature water supply pipe for return to a hot water heater.
2. Brief Description of the Prior Art
There is a great need to conserve natural resources such as water. Unfortunately, many potable water delivery systems are not designed to conserve water, rather these systems cause many gallons of water to be wasted.
Many potable water delivery systems, for example, deliver the fluid at both a "hot" and a "cold" temperature. In many of these delivery systems the water is heated by a water heating device which is located a considerable distance away from the location where the water is drawn from the delivery system. That is, the hot water faucet is located a considerable distance away from the water heater device.
Referring now to FIG. 1, which schematically illustrates a typical prior art potable water delivery system 100, potable water is inletted in the direction shown by an arrow 102, through a potable water supply pipe 103. At a T-joint 104, the potable water flows .through a cold water supply pipe 106 and through a water heater inlet pipe 108. The pipe 106 is in fluid communication with a cold water isolation valve 125.
The valve 125 is communicatively coupled, via a cold water riser pipe 127, to a cold water valve 114. The valves 125 and 114 are operated by handles 130 and 118, respectively. Potable water flowing through the pipe 106 flows through the valves 125 and 114 and, through a cold water spout 116 into a basin or sink 126.
The pipe 108 is communicatively coupled to a water heater 110. Potable water flows into the heater 110 where it is heated to a predetermined temperature level. The heater 110 is in fluid communication, via a hot water supply pipe 112, with a hot water isolation valve 128. Valve 128 is communicatively coupled, via a hot water riser pipe 129, to a hot water valve 120. The valves 120 and 128 are operated by handles 132 and 124, respectively. Potable water flowing through pipe 108 is heated by the heater 110 and flows through the pipe 112 through the valves 128 and 120, and through a hot water spout 122 into the sink. It should be further noted that the valves 125 and 128 are located beneath the sink 126, while the valves 114 and 120 are located above the sink 126.
Typically, there is infrequent use of hot potable water. Consequently, the water in the pipes 112 and 129 loses its heat through convective heat transfer with the ambient environment. Insulation wrapped about the pipes 112 and 129 may reduce the heat transfer through the pipe walls, but eventually the water in pipes 112 and 129 becomes cold. That is, the temperature of the water initially drawn from the spout 122 is unsatisfactorily cold for "hot" water purposes (i.e. washing, or cleaning). The result is that when the valve 120 is opened, the "cold" water in pipes 112 and 129 is purged before "hot" water is available from spout 122. Normally this purged water is not saved and is allowed to flow into a drain and is wasted. The amount of the purged water that is wasted can be several gallons and depends on the frequency of hot water usage, the length and diameter of the pipes 112 and 129, the ambient temperature, and other factors.
There have been several different devices utilized in prior art liquid delivery systems to conserve water. One device, best characterized as a hot water recovery system, is epitomized by four U.S. Patents issued to Haws, U.S. Pat. Nos. 4,321,943 (issued Mar. 30, 1982), 4,518,007 (issued May 21 1985), 4,798,224 (issued Jan. 17, 1989), and 4,930,551 (issued Jun. 5, 1990). Haws teaches connecting the hot and cold water supply piping at a location slightly upstream of the hot and cold water valves. A pressure reducing valve, installed upstream of the hot water heater, maintains the hot water supply pressure at a lower level than the pressure in the cold water supply piping. When the hot water valve is closed, the pressure in the cold water piping is greater than the pressure in the hot water piping, causing the cold water to flow into the hot water piping thereby back-flowing the hot-cold water mix through the hot water supply piping and into the water heater. The water heater serves as an accumulator for the heated water. Cold water replaces hot water in the hot water supply piping thus no thermal energy is transferred from the fluid contained within the hot water supply piping to the environment. The shortcoming of this approach is that when the hot water faucet is opened, the hot water supply line must still be purged of the cold water which back-flowed into the hot water supply line. This device does not reduce the amount of cold water that must be purged (i.e. wasted) from the hot water supply line before usable hot water can be drawn from the faucet.
Yet other devices designed to conserve water in a liquid delivery system are disclosed in Vataru et al. U.S. Pat. No. 4,160,461 (issued Jul. 10, 1979), and Powers et al. U.S. Pat. No. 4,697,614 (issued Oct. 16, 1987). The common elements in the devices disclosed in these patents are an accumulator and a crossover pipe communicatively coupling the hot water supply piping to the cold water supply piping. In Powers et al., an accumulator installed in the crossover pipe receives the cold water from the hot water supply line. The cold water is stored in the accumulator until it is discharged out of the cold water spout as usable cold water. Thus, cold water from the hot water supply pipe is pumped into a storage container (i.e., accumulator) and saved for later use. The cold water is not wasted by pouring it down the drain. In Vataru et al., an accumulator stores the cold water received from the hot water supply line; the cold water is mixed with hot water eventually received from the hot water heater line; when the cold water is heated to a predetermined temperature level it is made available at the hot water faucet. The problem with these approaches is that a retrofit of existing plumbing installations is significantly complicated when an accumulator is a required component of the liquid delivery system. The installation of the accumulator into an existing delivery system is very likely beyond the capability of most homeowners and would require special knowledge or experience, or tools.
Yet another prior art apparatus is typified by Ellis U.S. Pat. No. 3,741,195 (issued Jun. 26, 1973). In Ellis, the water heater is installed beneath the vanity or sink thereby minimizing the length of the hot water supply pipe and the amount of cold water purged from the hot water supply line. This system is clearly impractical for a typical home where there are a plurality of basins, tubs, and showers. It would be highly impractical, not to mention prohibitively costly, to install an individual heater unit at the location of each basin, tub or shower.
Another device used to conserve water in liquid delivery system circulates water from the hot water supply pipe to the cold water supply pipe. Typical recirculation systems are disclosed in Peters U.S. Pat. No. 2,842,155 (issued Jul. 8, 1958), Zimmer U.S. Pat. No. 4,331,292 (issued May 25, 1982), and Imhoff et al. U.S. Pat. No. 5,009,572 (issued Apr. 23, 1991).
Referring now to FIG. 2 which schematically depicts a potable water delivery system with recirculation 200 as taught by Peters and Zimmer. A crossover pipe 202 has been installed in the delivery system 100 (FIG. 1) and communicatively couples the hot water riser pipe 129 to the cold water riser pipe 127. The pipe 202 includes a bypass device 208, an inlet pipe 220, and an outlet pipe 222. One end of the inlet pipe 220 is mechanically connected to a T-joint 206 installed in the riser pipe 129. The other end of the inlet pipe 220 valve is mechanically connected to an inlet port connection 207 disposed in the bypass device 208. In similar fashion, one end of the outlet pipe 222 is mechanically connected to a T-joint 212 installed in the riser pipe 127. The other end of the outlet pipe 222 valve is mechanically connected to an outlet port connection 209 disposed in the bypass device 208. Thus, the bypass device is communicatively coupled to the riser pipes 127 and 129. The bypass device includes a check valve 218 and a thermostatic valve 216.
In operation, if the temperature of the water in the hot water riser pipe 127 and the inlet pipe 220 is generally at the temperature level of the cold water in the cold water riser pipe 127 and the outlet pipe 222, then the thermostatic valve 216 opens thereby allowing the water to circulate, in the direction shown by arrow 226, from the hot water riser pipe 129 to the cold water riser pipe 127. The water in the hot water supply pipe 112 is circulated, in the direction shown by an arrow 224, into the pipe 106 (FIG. 1) which now functions as a cold water supply/return pipe 201. Water recirculates in this manner until the water in the water flowing through the riser pipe 129 and the pipe 220 reaches a predetermined temperature level. When the predetermined temperature level is reached, the valve 216 closes thereby preventing the water from circulating into the piping 222 and 201. When valve 216 closes, water, in the pipe 112, flows in the direction of an arrow 228, through the riser pipe 129, through the valve 120 and through the spout 122 into the sink 126. Water, in the pipes 112 and 129, is not purged from the system but is circulated within the system until it is heated to a usable temperature level.
The problem with these devices is that they depend on the density difference between the hot and cold water to provide a pressure head that will cause a convection flow through the crossover pipe. This implies that the hot water heater must be at a lower elevation than the faucet. The absence of a pump in the Peters and Zimmer devices creates doubt that these devices will work properly.
In Imhoff et al., a crossover device similar to the Peters and Zimmer devices, connects the hot and cold water supply pipes. Referring now to FIG. 3, which schematically illustrates a potable water delivery system with pumped recirculation 300 taught by Imhoff et al. A crossover pipe 301 has been installed in the delivery system 100 (FIG. 1) and communicatively couples the hot water riser pipe 129 to the cold water riser pipe 127. The pipe 301 includes a solenoid valve 304, a thermostat 306, a pump 308, a temperature sensor 310, a pipe 312, a pipe 314, an inlet pipe 321, and an outlet pipe 323. An enclosure 302 houses the valve 304, the thermostat 306, the pump 308 and the sensor 310. One end of the inlet pipe 321 is mechanically connected to the T-joint 206 installed in the riser pipe 129. The other end of the inlet pipe 321 valve is mechanically connected to the temperature sensor 310. The sensor 310 is communicatively coupled, via the pipe 312, to the pump 308. The pump 308 is communicatively coupled, via the pipe 314, to the solenoid valve 304. In similar fashion, one end of the outlet pipe 323 is mechanically connected to the T-joint 212 installed in the riser pipe 127. The other end of the outlet pipe 323 valve is mechanically connected to the solenoid valve 304. Thus, the crossover pipe 301 is communicatively coupled to the riser pipes 127 and 129. In addition, the thermostat 304 is communicatively coupled to the pump 308 (via a pump energize signal line 318), to the temperature sensor 310 (via a temperature level signal line 316), to the solenoid valve 304 (via a valve energize signal line 320). Finally, AC power to the system is provided from a wall outlet 328 with two receptacles 326 and 327 that are located beneath the sink 126 and in close proximity to the crossover pipe 302. One end of a power cord 322 is communicatively coupled to the thermostat 306. The other end of the cord 322 is fitted with a standard three-prong plug 324 which can be inserted into the receptacle 326.
In operation, the plug 324 is inserted into the receptacle 326, thereby supplying power to the electrical components (i.e., valve 304, pump 308, sensor 310, and thermostat 306) installed on the pipe 301. If the temperature of the water in the pipes 321 and 129, as sensed by the sensor 310, is below a predetermined level the sensor 310 will generate a temperature level signal and transmit it over the signal line 316. The thermostat 306, in response to the signal, will energize the pump 308, and energize and position the solenoid valve 304 to allow the water to be circulated from the hot water riser pipe 129, through the crossover pipe 301, and into the cold water riser pipe 127. Water is circulated from the hot water supply to the cold water supply piping, in the general direction of the arrows 224 and 226, until the water heats up to the predetermined temperature level. When the temperature sensor 310 senses that the water in the hot water supply riser pipe 129 and the inlet pipe 220 is at the predetermined level, then the sensor 310 transmits a new temperature signal over the signal line 316. In response to the new signal, the thermostat 306 de-energizes the pump 308 (via signal line 318) and de-energizes the solenoid valve 304 (via the signal line 320) thereby positioning the valve 304 to stop the water flow through the crossover pipe 302. The water, at the predetermined temperature level (i.e. "hot" water) flows, in the general direction of the arrow 228, through the hot water riser pipe 129 and out of the spout 122.
The major problem with the Imhoff et al. device is that electrical components (i.e. the pump, solenoid valve, thermostat, and sensing device) are installed in the crossover pipe. When the crossover pipe is installed beneath existing sinks, basins, tubs, or showers both mechanical and electrical connections must be made. In addition, an electrical power outlet must be in close proximity to the crossover pipe in order to supply power to operate the pump and the other electrical components. If a crossover pipe as disclosed by Imhoff et al. is used to conserve water in an existing liquid delivery system, the retrofit installation of the crossover pipe into the delivery system will be needlessly complex and difficult.